Differences in hepatic gene expression between lactating and non-lactating sows as assessed by genome-wide transcript profiling

Background: While the mechanisms underlying the lactation-induced adaptations of intermediary metabolism and immune response have been extensively studied in rodents and dairy cows, little is known in this regard in sows. Therefore, the present study aimed to explore the lactation-induced changes in hepatic gene expression in sows during lactation. Results: Using a porcine whole-genome microarray a total of 632 differentially expressed genes in the liver of lactating compared to non-lactating sows (each n = 10) could be identified. Enrichment analysis revealed that the differentially expressed genes were mainly involved in fatty acid metabolism, pyruvate metabolism, glutathione metabolism, glycine, serine and threonine metabolism, citrate cycle, glycerophospholipid metabolism, PPAR signaling, nitrogen metabolism, and focal adhesion. The most striking observation with respect to intermediary metabolism was that genes involved in fatty acid catabolism, the catabolism of gluconeogenic amino acids, the citrate cycle and the respiratory chain were up-regulated in the liver of sows during lactation. With respect to immune response, it could be demonstrated that genes encoding acute phase proteins and genes involved in tissue repair were up-regulated and genes encoding focal adhesion molecules were down-regulated in the liver of sows during lactation. Conclusion: The results from this study indicate that energy-generating pathways and pathways involved in the delivery of gluconeogenic substrates are induced in the liver of sows during lactation. The alterations of expression of genes encoding proteins involved in immune response suggest that lactation in sows may cause an adaptive immune response which possibly counteracts hepatic inflammation. For microarray analyses, four RNA pools each, for the non-lactating group (n = 4) and the lactating group (n = 4), were prepared from eight individual sows per group. To each RNA pool, RNA from two different sows per group contributed identical amounts of RNA.